The present invention generally relates to fire barriers for use in dynamic voids formed in buildings, and more particularly, pertains to systems that are capable of maintaining an effective barrier against the spread of fire despite a substantial relative displacement or distortion of the surfaces that define such voids.
A variety of dynamic voids or joints are typically incorporated in a building in order to prevent damage as the structure undergoes movement due to thermal, wind and seismic loads. In order to prevent the spread of heat, smoke, and flames therethrough, it is necessary to fit such voids with fire barriers. It is especially important for a fire barrier fitted to a joint to remain in tact after the joint has undergone substantial displacement or distortion due to seismic activity, as the risk of fire is acute immediately following an earthquake.
Various barrier systems have been devised that attempt to accommodate the magnitude of movement anticipated during a seismic event. A substantial widening and/or narrowing, as well as substantial lateral or shear displacement of a seismic joint can be expected. Fire barriers typically consist of a sheet of flexible material that is attached to each wall of the joint and loosely draped therebetween. Such configuration does not in any way impede the narrowing of the gap while the slack in the material accommodates a widening of the gap beyond its nominal width. Its inherent flexibility also allows the material to take up any differential vertical displacement between the two sides of the joint. Despite being flexible, the previously used barrier materials are, however, substantially less capable of accommodating relative lateral displacement between the sides of the joint, and are prone to shear failure. In an effort to address this shortcoming, various complex mechanisms have additionally been developed in order to allow one or both sides of the barrier to shift along the walls of the joint. Some configurations provide for the barrier to be rigidly affixed to one side of the joint while the opposite edge of the barrier is slideably retained in a groove or track attached to the opposite wall of the joint. Alternatively, both edges of the barrier are retained within grooves or tracks formed in both sides of the joint in order to allow both sides to shift laterally relative the walls of the joint.
These prior art fire barrier systems suffer from a number of disadvantages. The complexity of many of such systems renders their initial cost rather high. Moreover, installation of a complex system is often more difficult, especially for retrofitment to existing buildings thereby further increasing the overall cost. Finally, the various mechanisms that allow such systems to accommodate lateral displacement typically rely on various moving parts that would require periodic maintenance. The prior art is therefore substantially devoid of a simple, low cost, low maintenance barrier system that is easily installed and that is capable of accommodating relative lateral displacement.